Tag: Electrical Systems
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Equipment Grounding vs. System Grounding
Grounding or earthing an electrical system is the process of connecting all metalwork/frame of electrical equipment i.e. the non-current carrying part or some electrical component of the system such as the neutral point in a star-connected system, one conductor of the secondary of a transformer, and so forth to the main body of earth. An…
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Switchgear Terminology & IEC Standards
Switchgear generally refers to the switching devices and their combinations, with the related control, measuring, protective and regulating equipment. The switchgear equipment basic purpose is switching and interrupting currents either under normal or abnormal operating conditions. Modern power systems, power lines and other apparatus operate at high voltages and carry large currents. When a short…
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Testing & Commissioning Protective Schemes
Generally protective equipment testing may be divided into three stages: Factory and commissioning tests confirm the performance of equipment during its development and fabrication, and its operational environment. Periodical maintenance ensures that this performance is maintained. For example, the relay manufacturer must provide sufficient testing of protective gear before it is accepted and commissioned. The…
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Residential Electrical Wiring: Key Safety Considerations
Residential Electrical Wiring Overview A residential electric power service typically consists of a three wire ac system supplied by the local power utility company. A distribution transformer with a primary and two secondaries formed with a center tap on the secondary side is shown below: The distribution transformer is located on the utility pole, from…
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Protective Relays: Function, Features & Operation
A protective relay is basically an electrical device that detects a fault in a power system and initiates the operation of the circuit breaker to isolate the defective section or component from the rest of the system. In other words, the prime function of protective relays is the timely and discriminative clearance of system faults.…
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SF6 Circuit Breakers: Features, Operation & Applications
Introduction Many modern designs of circuit breakers for use at transmission voltages utilize sulphur hexafluoride (SF6) gas both as an arc-interrupting/arc-quenching and a dielectric medium. At distribution voltages SF6 designs of circuit breakers are also used, however vacuum and bulk-oil circuit breakers still find a wide use as alternatives. The SF6 is an electron-negative gas…
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How Ground Fault Interrupter (GFI) is used as a Safety Device
The function of a ground fault interrupter (GFI) is to disconnect the power if a current leakage to ground is detected. GFI is also termed to as Ground fault circuit interrupter (GFCI). We have two types of ground fault interrupters: those designed for life protection and those designed for equipment protection. GFI used for life…
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Switchgear Equipment
Switchgear can be defined as equipment used for controlling, regulating and switching ON and OFF power circuits. Switchgear units range from the small moulded-case unit circuit breakers in a household panel board to the huge, air break switches on 750 kV transmission lines. Switchgear equipment is generally divided into four groups, namely: Disconnect/Isolator Switches Disconnect…